Continuity mistake: In one episode, there is a bowl of fruit on the table in the living room. The boys start wrestling and they knock it down. In the next shot it's back on the table again, untouched.
Continuity mistake: During the show's first two seasons, we are told Roseanne had a more slender figure during her younger years and didn't start gaining weight until after she began having kids. Later in the Halloween episode, "The Ghost of Halloween Past," Roseanne is shown her past, and her younger versions are not slender.
Continuity mistake: In episodes when Darlene has just moved into her apartment, the bathtub is on the wall in front of the bathroom door. In later episodes, the tub is on the wall to the left of the door.
Continuity mistake: In "Guilty By Suspicion," Jackie hangs up her coat in her living room closet. This is the same door that, when she first moved into the house, led to the basement.
Continuity mistake: In the episode where Jackie takes over the house, while Roseanne is at their parents. DJ comes in the kitchen and is sent in the laundry area for a shirt. Before he goes in there he is wearing a pair of dark jean with nothing on them. He comes back a second later with his head stuck in a shirt still with the same pants on. But when he finally pops his head through the shirt his pants have changed to a pair of stonewash, with what looks like bleach stains on the front. A wide shot of the kitchen in the next frame and his pants are back to the dark ones with nothing on them.
Answer: Clearly, the only person who could truly answer this question would be a set designer for the series, or someone else directly connected to the series who would have this kind of detailed information. I looked on IMDb.com and Cheryl Lanner is credited as set designer through 1997. I quickly found her Facebook page, and I directed your question to her. After some time, Ms. Lanner has replied as follows: "I decorated the last season 1/2 but after 9 seasons the sofa just plain got worn out and had to be repaired from 8 years of usage. There was a board put on the sofa but as I've said, it was due to so much usage. If they had back problems I was unaware of them, but you can be assured that if that was the problem it would have been fixed immediately. Take care Michael!"
Michael Albert